Resurfacing the charging contacts?

Hey! I wear my bangle.js every day, also when doing sports etc... and I guess over time all the motion and bodily fluids and the charging cable are beginning to eat away the charging contacts. What could I do to restore them before the contacts are fully gone?

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If you care only about charging then only the outer two are relevant. The middle two are for low level SWD debugging, if you don't plan to use that, you can cover with tape or paint the green one with nail polish or something

The green one is the one causing all this as it has 3.3V on it so it is the only one worth covering.

see also https://www.espruino.com/Bangle.js2+Technical#swd

Thanks @fanoush, I had sticky tape on the middles ones, but the tape keeps disappearing.

So you're saying the the other pads are affected by the 3.3V pad and this is why the others are also disintegrating?

Maybe it's not clear on the photo, but the brownish part on the outer pads is actually the color of the PCB, meaning that the pads are almost gone. Could I add a tiny drop of solder there? Would that allow me to charge still?

So you're saying the the other pads are affected by the 3.3V pad and this is why the others are also disintegrating?

yes, the SWDIO having 3.3V due to internal pull up causes current to flow when you sweat causing electrolysis

as for the rest I don't know, I'd guess there is no PCB there but copper rod going through but I did not have the watch opened so I don't know, I wouldn't risk with solder as long as it still works, it could make it worse

BTW here https://ibb.co/zhgyjV4 is my watch that I wear daily since the early days of bangle.js 2 and I never covered those pins. I don't do a lot of heavy sports with it but I do wear it during summer hiking in hot weather so it can have like 1 month in a year when I sweat quite a bit more with it. Interesting is that for me the other pins are unaffected, just the SWDIO looks bad.

Hi. I have the same problem. I have used mine for running 4 days a week for around a year and a half. I had the two internal contacts covered as sold by Espruino, but it seems the sweat has filtered under it. The charging contacts are also corroded. I thought that the contacts where from a connector and not a PCB, something like this:

https://www.olimex.com/Products/Components/Cables/USB-MAG-4-PCB/

Ideally we should remove the corroded plating to expose the base metal, then make nickel plating and on top of that gold plating. Because buying the chemicals for just four contacts is expensive and the chemicals seem to be pretty nasty, what I want to do is tinning the contacts with a soldering iron. I was going to do it tomorrow, I can record it and upload the video if the contacts make good connection again.

what I want to do is tinning the contacts with a soldering iron

I would be afraid of melting/burning the plastic around it. Also I am not sure how stable and healthy/allergic is solder - it is not just Sn but other metals (possibly even lead) and also flux and other chemicals. Also tin is relatively soft and may oxidize too.

I would be afraid of melting/burning the plastic around it.

I will apply the solder with solder wick, not directly with the soldering iron. I know I could cause some damage to the plastic, but the problem is that the watch is not charging anymore.

Also I am not sure how stable and healthy/allergic is solder - it is not just Sn but other metals (possibly even lead) and also flux and other chemicals. Also tin is relatively soft and may oxidize too.

The solder is lead-free. I will clean the flux after the work and I'm going to start using the silicone cover, not only to protect my skin, but also to reduce oxidation as much as possible.

As I said, nickel-gold plating would be ideal, but I don't think I'm going to follow that route.

How about trying a conductive glue/paint? Those usually contain silver, copper or graphite and could maybe even removed with a solvent if does not work. You should be able to get tiny amounts for a few dollars on ebay or aliexpress. Graphite/carbon based would probably be the most corrosion resistant and the least conducting.